Atomic Structure Flashcards
Mass number
Total number of protons and neutrons
Atomic number
The number of protons in an atom of an element
Isotope
Atoms with the same number of protons but different number of neutrons
JJ Thompson
Plum pudding -
Atom consisted of positive “dough” with negative electrons
Ernest Rutherford
Gold foil experiment (Nuclear model of the atom) -
Shoot alpha particles at a gold foil to see if they go through or bounce back, as a result, he discovered the nucleus
Niels Bohr
Electrons orbiting -
He discovered that electrons orbit the nucleus at a fixed distance
James Chadwick
Neutron -
He discovered the neutron
Alpha particle
Contain two neutrons and two protons (helium atom)
Low penetration as they are big, heavy and slow
Stop quickly when traveling through the air
However, they are strongly ionising (when they collide with atoms to create ions)
Beta particles
They are electrons
Move quite fast and are small
Penetrate moderately and have a long-range in the air with their ionising ability being moderate
Gamma rays
They are very short-wavelength electromagnetic waves
Penetrate far into materials and pass straight through the air, therefore they are weakly ionising
They have no mass or charge
Radioactive
A substance containing unstable nuclei that becomes stable by emitting radiation
Background radiation
Radiation that is present at all times
E.g. food (bananas), x-rays, and cosmic rays from the Sun
Half-life
The time taken for the number of radioactive nuclei in a substance to halve
Carbon dating
Uses radioactive carbon to identify the age of organic material
Uses of nuclear radiation
Medicine
X-rays
Nuclear fission
Neutron hits the uranium nucleus
Uranium nucleus splits into smaller nuclei and some more neutrons
These neutrons hits more uranium nuclei and the process continues
Nuclear fusion
When two small, light nuclei join together to make one heavy nucleus
Contamination
Occurs if an object has a radioactive material introduced into (or onto) it
A contaminated object will be radioactive for as long as the source is on or in it
Once an object is contaminated, the radiation cannot be blocked from it
Irradiation
Occurs when an object is exposed to a source of radiation outside the object
Doesn’t cause the object to become radioactive
Can be blocked with suitable shielding or moving away
